Power boat propulsion system

ABSTRACT

A power boat propulsion system installed in a power boat having a waterway in the stern, an engine on the inside, and a shaft coupled to the engine and inserted through the waterway, includes a barrel-like impeller duct fixedly fastened to the rear outlet of the waterway, an impeller pivoted to the inside of the impeller duct and connected to the shaft for synchronous rotation with the shaft, a stator mounted inside the impeller duct and adapted for supporting a rear end of the shaft, and a rudder mounted inside the impeller duct near a rear outlet of the impeller duct. The rudder has top and bottom sides thereof pivoted to the impeller duct for deflection leftwards and rightwards.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to power boats and, more specifically, to a propulsion system for a power boat.

[0003] 2. Description of the Related Art

[0004]FIG. 1 illustrates a conventional inboard engine type power boat. According to this design, the propulsion system of the power boat comprises an engine 81 mounted inside the body of the boat, a shaft 82 coupled to the engine 81 and extended obliquely downwardly to the outside of the boat below the foot of the boat, an impeller 83 fastened to the rear end of the shaft 82, and a rudder 84 pivoted to the foot of the boat near the stern of the boat. When started the engine 81, the impeller 83 is rotated with the shaft 82 in water, producing a propulsive force to propel the boat forwards. This design is less efficient because the propulsive force is not fully concentrated to one direction. The propulsion system of an outboard engine type power boat has the same drawback.

[0005]FIG. 2 illustrates a power boat waterjet propulsion system according to the prior art. According to this design, a tubular waterway 92 is suspended from the stern of the body 91 of the boat and extended backwards from the bottom side of the boat, an engine (not shown) mounted inside the body 91 of the boat, a shaft 93 coupled to the engine and extended through the waterway 92 to the rear outlet, a barrel-like impeller duct 94 fixedly fastened to the rear side of the waterway 92, a stator 96 fixedly mounted inside the impeller duct 94, an impeller 95 fastened to the rear end of the shaft 93 in the impeller duct 94 and pivoted to the stator 96, a jet nozzle 97 disposed in the rear side of the impeller duct 94 and deflectable leftwards rightwards, and a lifting guide hood 98 suspended near the rear side of the impeller duct 94. When the impeller 95 rotated with the shaft 93, water is sucked from the bottom side of the waterway 92 into the inside of the impeller duct 94 and then guided by the stator 96 into an axial flow, and then ejected backwards through the jet nozzle 97 to propel the boat forwards. By means of controlling the angle of deflection of the jet nozzle, the sailing direction of the boat is relatively controlled. When the lifting guide hood 98 lowered, the jet flow of water is forced forwards, thereby causing the boat to move backwards. This design of waterjet propulsion system is still not satisfactory in function. The drawbacks of this design of waterjet propulsion system are numerous and outlined hereinafter.

[0006] 1. The whole structure of the system is complicated and expensive to manufacture because it is made of metal.

[0007] 2. The whole system is bulky and heavy, not convenient for installation, and affecting the propulsion efficiency.

[0008] 3. It requires much power to control deflection of the jet nozzle.

[0009] 4. The high speed and low volume jet water produced during the operation of the propulsion system affects the performance of the boat during a middle or low speed sailing.

SUMMARY OF THE INVENTION

[0010] The present invention has been accomplished to provide a power boat propulsion system, which eliminates the aforesaid drawbacks. It is one object of the present invention to provide a power boat propulsion system, which has a simple structure, compact size, and light weight.

[0011] It is another object of the present invention to provide a power boat propulsion system, which controls the boat to change the direction efficiently.

[0012] It is still another object of the present invention to provide a power boat propulsion system, which produces a low pressure and high flow rate axial flow of water during operation, suitable for a boat drawing less amount of water.

[0013] To achieve these objects of the present invention, the power boat propulsion system is installed in a power boat, which comprises a waterway extended from the foot of the boat to the stern thereof, an engine mounted on the inside, and a shaft coupled to the engine and inserted through the waterway to a rear outlet of the waterway. The propulsion system comprises a barrel-like impeller duct having a front inlet fixedly coupled to the rear outlet of the waterway and a rear outlet for output of water from the waterway, an impeller pivoted to the inside of the impeller duct and connected to the shaft for synchronous rotation with the shaft, a stator mounted inside the impeller duct and spaced from the impeller at a rear side and adapted for supporting a rear end of the shaft, and a rudder mounted inside the impeller duct near the rear outlet of the impeller duct. The rudder has top and bottom sides thereof pivoted to the impeller duct for deflection leftwards and rightwards.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 illustrates an inboard engine type power boat according to the prior art.

[0015]FIG. 2 is a schematic drawing showing the arrangement of a power boat waterjet propulsion system according to the prior art.

[0016]FIG. 3 is a schematic drawing showing a propulsion system installed in a power boat according to a preferred embodiment of the present invention.

[0017]FIG. 4 is an enlarged view of a part (right side) of FIG. 3.

[0018]FIG. 5 is a rear side view of the propulsion system according to the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] Referring to FIG. 3, a propulsion system 10 is mountable to the stern of a power boat 20 that does not draw much water and, is not for sailing at a high speed (remark: the sign “L” shown in FIG. 1 indicates the water surface). The boat 20 comprises a recessed portion 21 in the stern below the waterline, a waterway 24 disposed in the rear portion of the boat and smoothly upwardly extended from the foot of the boat to a front sidewall 22 of the recessed portion 21 (see also FIG. 4). An engine 25 is installed inside the body of the boat 20. A shaft 26 is coupled to the engine 25 and inserted through the waterway 24 to the rear outlet of the waterway 24. Unlike the conventional design of attaching a metal waterway to the boat, the waterway 24 is formed of a part of the fiber reinforced plastic body of the boat 20.

[0020] Referring to FIGS. 4 and 5, the propulsion system 10 comprises a barrel-like impeller duct 11, an impeller 14 pivoted to the inside of the impeller duct 11 and connected to the shaft 26 for synchronous rotation with the shaft 26, a stator 15 fixedly mounted inside the impeller duct 11 behind the impeller 14 to support the rear end of the shaft 26, and a rudder 16 mounted inside the impeller duct 11 near the rear outlet of the impeller duct. The rudder 16 has top and bottom sides respectively pivoted to the inside wall of the impeller duct 11 for deflection leftwards/rightwards (for deflection in either direction within 50°). The impeller duct 11 has a smoothly arched top side and a flat bottom side, two skegs 12 bilaterally protruded from the bottom sidewall thereof and respectively downwardly reduced in thickness, and two connecting arms 13 upwardly obliquely extended from the top sidewall thereof near the rear side. The internal space of the impeller duct 11 has a substantially cylindrical shape with a relatively greater front half and relatively smaller and tapered rear half. The rear outlet of the impeller duct 11 has a circular shape. The impeller duct 11 is inserted into the recessed portion 21 of the power boat 20 with its front side fixedly fastened to the front sidewall 22 of the recessed portion 21 and its front inlet coupled to the rear outlet of the waterway 24. Further, the two connecting arms 13 of the impeller duct 11 are fixedly fastened to the top sidewall 23 of the recessed portion 21 of the power boat 20.

[0021] Further, a linkage 30 is provided in the recessed portion 21 of the power boat 20 above the impeller duct 11 and coupled between the control system (not shown) of the power boat 20 and the rudder 16, for enabling the control system of the power boat 20 to control the deflection of the rudder 16. Because the linkage 30 is of the known mechanism and not within the scope of the claims of the present invention, no further detailed description is necessary.

[0022] When the impeller 14 rotated with the shaft 26, water is sucked from the bottom inlet of the waterway of the power boat 20 into the impeller duct 11 through the waterway 24, and then guided by the stator 15 into an axial flow and then ejected out of the recessed portion 21 through the rear outlet of the impeller duct 11. When turned the rudder 16 to the left right direction in axial alignment with the power boat 20, the axial flow of water is freely ejected out of the impeller duct 11 to propel the power boat 20 forwards. When biased the leading edge of the rudder 16 toward the left, the axial flow of water is biased toward the right, thereby causing the power boat 20 to be turned to the right. On the contrary, when biased the leading edge of the rudder 16 toward the right, the axial flow of water is biased toward the left, thereby causing the power boat 20 to be turned to the left. When wishing to reduce the speed of the power boat 20 or to stop the power board 20, reduce the revolving speed of the impeller 14, or stop/reverse the impeller 14.

[0023] In comparison with the prior art designs, the propulsion system of the present invention provides the following advantages:

[0024] 1. having a simple design and low manufacturing cost;

[0025] 2. having a compact structure and light weight, convenient for mounting and dismounting, greatly reducing the total weight of the boat and improving the propelling efficiency;

[0026] 3. requiring less torsional force to deflect the rudder in the impeller duct; and

[0027] 4. being practical for high speed sailing as well as low speed sailing because of low pressure and high flow rate jet water. 

What is claimed is:
 1. A power boat propulsion system installed in a power boat, said power boat comprising a waterway extended from the foot to the stern thereof, an engine mounted in the inside of the boat, and a shaft coupled to said engine and inserted through said waterway to a rear outlet of said waterway, the propulsion system comprising: a barrel-like impeller duct having a front inlet fixedly coupled to the rear outlet of said waterway and a rear outlet for output of water from said waterway; an impeller pivoted to the inside of said impeller duct and connectable to said shaft for synchronous rotation with said shaft; a stator mounted inside said impeller duct and spaced from said impeller at a rear side and adapted for supporting a rear end of said shaft; and a rudder mounted inside said impeller duct near the rear outlet of said impeller duct, said rudder having top and bottom sides thereof pivoted to said impeller duct for deflection leftwards and rightwards.
 2. The power boat propulsion system as claimed in claim 1, wherein said power boat comprises a recessed portion in the stern below the waterline; said waterway is disposed in the foot of said power boat and smoothly upwardly extended from the foot of said power boat to a front sidewall of said recessed portion; said impeller duct has a front side fixedly fastened to the front sidewall of said recessed portion, and at least one connecting arm disposed at a top side and respectively fixedly fastened to a top sidewall of said recessed portion.
 3. The power boat propulsion system as claimed in claim 1, wherein said impeller duct defines substantially a cylindrical internal space, and has a flat bottom sidewall.
 4. The power boat propulsion system as claimed in claim 1, wherein said rubber is deflectable leftwards and rightwards within 50° in each direction. 